A “green” variation of the Hirao reaction: the P–C coupling of diethyl phosphite, alkyl phenyl-H-phosphinates and secondary phosphine oxides with bromoarenes using a P-ligand-free Pd(OAc)₂catalyst under microwave and solvent-free conditions

Abstract

The general value of the title reaction affording diethyl arylphosphonates, alkyl diphenylphosphinates and tertiary phosphine oxides was demonstrated.

The Use of MW in Organophosphorus Chemistry

“…The similar reaction of alkyl phenylpropiolates and two equivalents of dialkyl phosphites at 190°C afforded a mixture of E and Z alkyl 3-(dialkoxyphosphoryl)-3-phenylacrylates (43), and in a few cases some of the bisadducts (44). Within the phosphoryl-phenylacrylates (43) the E isomer predominated (Scheme 3.30, Table 3.8) [62].…”

“…It was interesting to find that there is no need to use the expensive Pd(Ph 3 P) 4 catalyst in the coupling reaction of dialkyl phosphites with bromobenzene, as Pd(OAc) 2 also catalyses the Hirao reaction in the absence of any added P-ligand. A MW-assisted solvent-free accomplishment was the best choice [42,43]. The arylphosphonates (30) were obtained in 69-93 % yields (Scheme 3.17).…”

Microwave-assisted Hirao reaction: recent developments

“…In the very next year, Keglevich group have extended the same reaction with more variety of both the substrates, thereby offering the reaction a general value [32]. Thus such a P-ligand-free variation of the microwave-assisted Hirao reaction proves to be a generally useful and ecofriendly method.…”

A DFT study on the reaction mechanisms of phosphonation of heteroaryl N-oxides with H-phosphonates

“…Since the palladium-catalyzed cross-coupling reaction of dialkylphosphites with aromatic halides has been reported by Hirao and co-workers in the early eighties [2,3], it has been widely used in the formation of phosphorus-carbon bond [4][5][6][7]. Subsequently, more and more methods for preparation of heteroaryl phosphonates have been discovered in recent years.…”